MATLAB Array and String Functions

Built-in Functions for Handling Arrays

• diag(v) creates a square matrix with zeroes, except for the main diagonal which is populated by the elements of vector v.
• diag(A) creates a vector containing the elements of the main diagonal of matrix A.
• For more array handling functions, navigate through the help icon in MATLAB: MATLAB -> MATLAB Functions -> By Category -> Matrices and Arrays.

Strings

• A string is an array of characters.
• Strings in MATLAB are used for:
  • Displaying text output
  • Specifying plot formatting
  • Inputting arguments for functions
  • Text input from user or data files
• Strings are created by typing characters within single quotes ('). Other programming languages typically use quotation marks (").
• Text color changes to maroon when typing the first single quote and purple when typing the last single quote.

Strings: Characters & Symbols

• Strings can contain letters, digits, symbols, and spaces.
• Single quotes within a string can be represented using two consecutive single quotes (')
• Examples of strings: 'ad ef', '3%fr2', 'edcba:21!', 'MATLAB'.

String Variables

• Strings can be assigned to variables like numbers.
• Example:
  • name = 'Sting', police = 'New York''s finest'.

String Variables: Storage & Indexing

• Numbers in strings are stored as an array.
• A one-line string is a row vector, with the number of elements equaling the number of characters in the string.
• Example:
  • name = 'Howard the Duck' has 15 characters and thus a size of 1x15.
• Strings can be indexed and manipulated similarly to vectors and matrices. Elements can be read, written, and deleted by index.

String Variables: Example Operations

• Example:
  • word = 'dale', word(1) = 'v' changes the word to vale.
  • word(end) = [] removes the last character e from vale resulting in val.
  • word(end+1:end+3) = 'ley' adds ley to val, making it valley.

Multi-line Strings

• MATLAB stores multiline strings as arrays.
• Each line must have the same number of characters (columns).
• If lines have a different number of characters, MATLAB throws an error when combining them in a vertical array (names = ['Greg'; 'Jon']).
• To avoid errors, manually add spaces (or other characters) to make all lines the same length.
  • Example: names = ['Greg'; 'Jon '].

char Function

• char function overcomes the need for manual padding by adding enough spaces to each line on the right side to ensure all lines have the same number of characters.
  • Example: char('string 1', 'string 2', 'string 3').

char Function: Example Usage

• Example:
  • question=char('Romeo, Romeo,', 'Wherefore art thou', 'Romeo?') creates a multi-line string, where each line has exactly 18 characters due to the added space characters.

Matrices: Appending Elements

• To append matrices, the dimensions must match:
  • Adding a matrix to the right side of another matrix requires the same number of rows for both matrices.
  • Adding a matrix to the bottom of another matrix requires the same number of columns for both matrices.

Matrices: Appending Example

• Examples:
  • Z=[A2 B2] appends matrix B2 to the right of A2. Both have the same number of rows.
  • Z=[A2; C2] appends matrix C2 below matrix A2. Both have the same number of columns.
  • Z=[A2; B2] throws an error because A2 and B2 have different number of columns.

Matrix: Unassigned Elements

• Unassigned elements in matrices are set to zero by default.

• Example:

  • Matrix BG initially has only a few elements populated. When a new element BG(3,4) = 15 is assigned, the other elements retain their default value of zero.

This quiz covers built-in functions in MATLAB for handling arrays and strings. It focuses on creating square matrices, extracting main diagonals, and understanding string functionalities. Test your knowledge on these essential MATLAB concepts!